Revert "Refactor commitPlacement to recursively insert nodes (#17996)" (#18517)

This reverts commit df5fadd.

Author: gaearon

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -1283,72 +1283,44 @@ function commitPlacement(finishedWork: Fiber): void {
   const before = getHostSibling(finishedWork);
   // We only have the top Fiber that was inserted but we need to recurse down its
   // children to find all the terminal nodes.
-  if (isContainer) {
-    insertOrAppendPlacementNodeIntoContainer(finishedWork, before, parent);
-  } else {
-    insertOrAppendPlacementNode(finishedWork, before, parent);
-  }
-}
-
-function insertOrAppendPlacementNodeIntoContainer(
-  node: Fiber,
-  before: ?Instance,
-  parent: Container,
-): void {
-  const {tag} = node;
-  const isHost = tag === HostComponent || tag === HostText;
-  if (isHost || (enableFundamentalAPI && tag === FundamentalComponent)) {
-    const stateNode = isHost ? node.stateNode : node.stateNode.instance;
-    if (before) {
-      insertInContainerBefore(parent, stateNode, before);
-    } else {
-      appendChildToContainer(parent, stateNode);
-    }
-  } else if (tag === HostPortal) {
-    // If the insertion itself is a portal, then we don't want to traverse
-    // down its children. Instead, we'll get insertions from each child in
-    // the portal directly.
-  } else {
-    const child = node.child;
-    if (child !== null) {
-      insertOrAppendPlacementNodeIntoContainer(child, before, parent);
-      let sibling = child.sibling;
-      while (sibling !== null) {
-        insertOrAppendPlacementNodeIntoContainer(sibling, before, parent);
-        sibling = sibling.sibling;
+  let node: Fiber = finishedWork;
+  while (true) {
+    const isHost = node.tag === HostComponent || node.tag === HostText;
+    if (isHost || (enableFundamentalAPI && node.tag === FundamentalComponent)) {
+      const stateNode = isHost ? node.stateNode : node.stateNode.instance;
+      if (before) {
+        if (isContainer) {
+          insertInContainerBefore(parent, stateNode, before);
+        } else {
+          insertBefore(parent, stateNode, before);
+        }
+      } else {
+        if (isContainer) {
+          appendChildToContainer(parent, stateNode);
+        } else {
+          appendChild(parent, stateNode);
+        }
       }
+    } else if (node.tag === HostPortal) {
+      // If the insertion itself is a portal, then we don't want to traverse
+      // down its children. Instead, we'll get insertions from each child in
+      // the portal directly.
+    } else if (node.child !== null) {
+      node.child.return = node;
+      node = node.child;
+      continue;
     }
-  }
-}
-
-function insertOrAppendPlacementNode(
-  node: Fiber,
-  before: ?Instance,
-  parent: Instance,
-): void {
-  const {tag} = node;
-  const isHost = tag === HostComponent || tag === HostText;
-  if (isHost || (enableFundamentalAPI && tag === FundamentalComponent)) {
-    const stateNode = isHost ? node.stateNode : node.stateNode.instance;
-    if (before) {
-      insertBefore(parent, stateNode, before);
-    } else {
-      appendChild(parent, stateNode);
+    if (node === finishedWork) {
+      return;
     }
-  } else if (tag === HostPortal) {
-    // If the insertion itself is a portal, then we don't want to traverse
-    // down its children. Instead, we'll get insertions from each child in
-    // the portal directly.
-  } else {
-    const child = node.child;
-    if (child !== null) {
-      insertOrAppendPlacementNode(child, before, parent);
-      let sibling = child.sibling;
-      while (sibling !== null) {
-        insertOrAppendPlacementNode(sibling, before, parent);
-        sibling = sibling.sibling;
+    while (node.sibling === null) {
+      if (node.return === null || node.return === finishedWork) {
+        return;
       }
+      node = node.return;
     }
+    node.sibling.return = node.return;
+    node = node.sibling;
   }
 }